1. Field of the Invention
The present invention relates to an ultrasound sensor used to measure distance, and more particularly to a sensor for determining and indicating distances between vehicles and obstacles at close range with ultrasound techniques. The sensor has a unique shape that covers the entire width of the vehicle without being falsely activated by the reflected ground signal.
2. Description of Related Art
Distance measurement by ultrasound is very helpful for metropolitan drivers. Confined by limited parking spaces, most drivers have to depend on their skills to squeeze into a parking space. However, when backing or parking vehicles, drivers normally have blind spots, which can cause serious consequences. Therefore, an ultrasound sensor for detecting the distance to an object was introduced to the market for drivers to eliminat the dangers of the existence of blind spots. Related information about the ultrasound sensor can be seen in U.S. Pat. No. 4,500,977, issued to Gelhard on Feb. 19, 1985 and U.S. Pat. No. 4,437,032 also issued to Gelhard on Mar. 13, 1984. A conventional ultrasound sensor (80) used in vehicles for sounding an alarm when approaching obstacles usually is mounted at the center of a vehicle (90), as shown in FIG. 9. It is well known in the art that the sensitivity of the sensor (80) is adjustable and the shape of the emitted signal by the sensor (80) is circular. Therefore, for the purpose of covering the entire cross sectional area of the vehicle (80), the diameter of the emitted beam by the sensor (80) is adjusted to be b1, as shown in FIG. 10-A. However, when the ultrasound sensor (80) mounted on the vehicle (90) is activated, a portion of the signal will be reflected by the ground, which will initiate a false alarm informing the driver that the vehicle (90) is approaching a potential obstacle, as shown in FIG. 8-B. To eliminate the possibility of the activation of a false alarm, the sensitivity of the sensor (80) is adjusted to have a diameter b2 which is smaller than b1, as shown in FIG. 11-A. With such a beam diameter, the vehicle (90) is able to detect the distance from an obstacle effectively. However, both sides of the vehicle (90) become blind spots for the driver, due to the reduced diameter of the emitted beam by the sensor (80), as shown in FIG. 11-B.
It is notable from the above description that the conventional ultrasound sensor is not appropriate and thus an improvement to the ultrasound sensor is necessary.
To overcome the aforementioned problems, the invention provides an improved ultrasound sensor having a unique shape that is able to emit signal covering the entire cross sectional area of the vehicle without initiating a false alarm.
The present invention tends to provide an improved ultrasound sensor to obviate and/or mitigate the aforementioned problems.